by Dennis Overbye
(NYT) SCIENCE DESK
May 22, 2001, Tuesday
What was God doing before he created the
world? The philosopher and writer (and later saint) Augustine posed
the question in his ’’Confessions’’ in the fourth century, and then
came up with a strikingly modern answer: before God created the
world there was no time and thus no ’’before.’’ To paraphrase Gertrude Stein, there was no
Until recently no one could attend a lecture on astronomy and ask
the modern version of Augustine’s question -- what happened before
the Big Bang? -- without receiving the same frustrating answer,
courtesy of Albert Einstein’s general theory of relativity, which
describes how matter and energy bend space and time.
If we imagine the universe shrinking backward, like a film in
reverse, the density of matter and energy rises toward infinity as
we approach the moment of origin. Smoke pours from the computer, and
space and time themselves dissolve into a quantum ’’foam.’’
’’Our rulers and our clocks break,’’
explained Dr. Andrei Linde, a cosmologist at Stanford
University. ’’To ask what is before this moment is a
But lately, emboldened by progress in
new theories that seek to unite Einstein’s lordly realm with the
unruly quantum rules that govern subatomic physics -- so-called
quantum gravity -- Dr. Linde and his colleagues have begun to edge
their speculations closer and closer to the ultimate moment and, in
some cases, beyond it.
Some theorists suggest that the Big Bang was not so much a birth as
a transition, a ’’quantum leap’’ from some formless era of imaginary
time, or from nothing at all. Still others are exploring models in
which cosmic history begins with a collision with a universe from
All this theorizing has received a further boost of sorts from
recent reports of ripples in a diffuse radio glow in the sky,
thought to be the remains of the Big Bang fireball itself. These
ripples are consistent with a popular theory, known as inflation,
that the universe briefly speeded its expansion under the influence
of a violent antigravitational force, when it was only a fraction of
a fraction of a nanosecond old. Those ripples thus provide a useful
check on theorists’ imaginations. Any theory of cosmic origins that
does not explain this phenomenon, cosmologists agree, stands little
chance of being right.
Fortunately or unfortunately, that still leaves room for a lot of
’’If inflation is the dynamite
behind the Big Bang, we’re still looking for the match,’’ said
Dr. Michael Turner, a cosmologist at the University of Chicago.
The only thing that all the experts agree on is that no idea
works -- yet. Dr. Turner likened cosmologists to jazz musicians
collecting themes that sound good for a work in progress: ’’You
hear something and you say, oh yeah, we want that in the final
One answer to the question of what
happened before the Big Bang is that it does not matter because it
does not affect the state of our universe today. According to a
theory known as eternal inflation, put forward by Dr. Linde in 1986,
what we know as the Big Bang was only one out of many in a chain
reaction of big bangs by which the universe endlessly reproduces and
’’Any particular part of the
universe may die, and probably will die,’’ Dr. Linde said,
the universe as a whole is immortal.’’
Dr. Linde’s theory is a modification of
the inflation theory that was proposed in 1980 by Dr. Alan Guth, a
physicist. He considered what would happen if, as the universe was
cooling during its first violently hot moments, an energy field
known as the Higgs field, which interacts with particles to give
them their masses, was somehow, briefly, unable to release its
Space, he concluded, would be suffused with a sort of latent energy
that would violently push the universe apart. In an eyeblink the
universe would double some 60 times over, until the Higgs field
released its energy and filled the outrushing universe with hot
particles. Cosmic history would then ensue.
Cosmologists like inflation because such a huge outrush would have
smoothed any gross irregularities from the primordial cosmos,
leaving it homogeneous and geometrically flat. Moreover, it allows
the whole cosmos to grow from next to nothing, which caused Dr. Guth
to dub the universe ’’the ultimate free lunch.’’
Subsequent calculations ruled out the Higgs field as the inflating
agent, but there are other inflation candidates that would have the
same effect. More important, from the pre-Big-Bang perspective, Dr. Linde concluded, one inflationary bubble would sprout another, which
in turn would sprout even more. In effect each bubble would be a new
big bang, a new universe with different characteristics and perhaps
even different dimensions. Our universe would merely be one of them.
’’If it starts, this process can
keep happening forever,’’ Dr. Linde explained. ’’It can happen
now, in some part of the universe.’’
The greater universe envisioned by
eternal inflation is so unimaginably large, chaotic and diverse that
the question of a beginning to the whole shebang becomes almost
irrelevant. For cosmologists like Dr. Guth and Dr. Linde, that is in
fact the theory’s lure.
’’Chaotic inflation allows us to
explain our world without making such assumptions as the
simultaneous creation of the whole universe from nothing,’’ Dr.
Linde said in an e-mail message.
Trying to Imagine The Nothingness
Nevertheless, most cosmologists, including Dr. Guth and Dr. Linde,
agree that the universe ultimately must come from somewhere, and
that nothing is the leading candidate.
As a result, another tune that cosmologists like to hum is quantum
theory. According to Heisenberg’s uncertainty principle, one of the
pillars of this paradoxical world, empty space can never be
considered really empty; subatomic particles can flit in and out of
existence on energy borrowed from energy fields. Crazy as it sounds,
the effects of these quantum fluctuations have been observed in
atoms, and similar fluctuations during the inflation are thought to
have produced the seeds around which today’s galaxies were formed.
Could the whole universe likewise be the result of a quantum
fluctuation in some sort of primordial or eternal nothingness?
Perhaps, as Dr. Turner put it, ’’Nothing is unstable.’’
The philosophical problems that plague ordinary quantum mechanics
are amplified in so-called quantum cosmology. For example, as
Dr. Linde points out, there is a chicken-and-egg problem. Which came
first: the universe, or the law governing it? Or, as he asks, ’’If
there was no law, how did the universe appear?’’
One of the earliest attempts to imagine the nothingness that is the
source of everything came in 1965 when Dr. John Wheeler and
Bryce DeWitt, now at the University of Texas, wrote down an equation
that combined general relativity and quantum theory. Physicists have
been arguing about it ever since.
The Wheeler-DeWitt equation seems to live in what physicists have
dubbed ’’superspace,’’ a sort of mathematical ensemble of all
possible universes, ones that live only five minutes before
collapsing into black holes and ones full of red stars that live
forever, ones full of life and ones that are empty deserts, ones in
which the constants of nature and perhaps even the number of
dimensions are different from our own.
In ordinary quantum mechanics, an electron can be thought of as
spread out over all of space until it is measured and observed to be
at some specific location. Likewise, our own universe is similarly
spread out over all of superspace until it is somehow observed to
have a particular set of qualities and laws. That raises another of
the big questions. Since nobody can step outside the universe, who
is doing the observing?
Dr. Wheeler has suggested that one answer to that question may be
simply us, acting through quantum-mechanical acts of observation, a
process he calls ’’genesis by observership.’’
’’The past is theory,’’ he once
wrote. ’’It has no existence except in the records of the
present. We are participators, at the microscopic level, in
making that past, as well as the present and the future.’’
In effect, Dr. Wheeler’s answer to
Augustine is that we are collectively God and that we are always
creating the universe.
Another option, favored by many cosmologists, is the so-called many
worlds interpretation, which says that all of these possible
universes actually do exist. We just happen to inhabit one whose
attributes are friendly to our existence.
The End of Time
Just Another Card In the Big Deck
Yet another puzzle about the Wheeler-DeWitt equation is that it
makes no mention of time. In superspace everything happens at once
and forever, leading some physicists to question the role of time in
the fundamental laws of nature. In his book ’’The End of Time,’’
published to coincide with the millennium, Dr. Julian Barbour, an
independent physicist and Einstein scholar in England, argues that
the universe consists of a stack of moments, like the cards in a
deck, that can be shuffled and reshuffled arbitrarily to give the
illusion of time and history.
The Big Bang is just another card in this deck, along with every
other moment, forever part of the universe. ’’Immortality is here,’’
he writes in his book. ’’Our task is to recognize it.’’
Dr. Carlo Rovelli, a quantum gravity theorist at the University of
Pittsburgh, pointed out that the Wheeler-DeWitt equation doesn’t
mention space either, suggesting that both space and time might turn
out to be artifacts of something deeper.
’’If we take general relativity
seriously,’’ he said, ’’we have to learn to do physics without
time, without space, in the fundamental theory.’’
While admitting that they cannot answer
these philosophical questions, some theorists have committed pen to
paper in attempts to imagine quantum creation mathematical rigor.
Dr. Alexander Vilenkin, a physicist at Tufts University in
Somerville, Mass., has likened the universe to a bubble in a pot of
boiling water. As in water, only bubbles of a certain size will
survive and expand, smaller ones collapse. So, in being created, the
universe must leap from no size at all -- zero radius, ’’no space
and no time’’ -- to a radius large enough for inflation to take over
without passing through the in-between sizes, a quantum-mechanical
process called ’’tunneling.’’
Dr. Stephen Hawking, the Cambridge University cosmologist and
best-selling author, would eliminate this quantum leap altogether.
For the last 20 years he and a series of collaborators have been
working on what he calls a ’’no boundary proposal.’’ The boundary of
the universe is that it has no boundary, Dr. Hawking likes to say.
One of the keys to Dr. Hawking’s approach is to replace time in his
equations with a mathematical conceit called imaginary time; this
technique is commonly used in calculations regarding black holes and
in certain fields of particle physics, but its application to
cosmology is controversial.
The universe, up to and including its origin, is then represented by
a single conical-shaped mathematical object, known as an
instanton, that has four spatial dimensions (shaped roughly like
a squashed sphere) at the Big Bang end and then shifts into real
time and proceeds to inflate.
’’Actually it sort of bursts and makes
an infinite universe,’’ said Dr. Neil Turok, also from
Cambridge University. ’’Everything for all future time is
determined, everything is implicit in the instanton.’’
Unfortunately the physical meaning of imaginary time is not clear.
Beyond that, the approach produces a universe that is far less dense
than the real one.
Faith of Strings
Theorists Bring On The ’Brane’ Worlds
But any real progress in discerning the details of the leap from
eternity into time, cosmologists say, must wait for the formulation
of a unified theory of quantum gravity that succeeds in marrying
Einstein’s general relativity to quantum mechanics -- two views of
the world, one describing a continuous curved space-time, the other
a discontinuous random one -- that have been philosophically and
mathematically at war for almost a century. Such a theory would be
able to deal with the universe during the cauldron of the Big Bang
itself, when even space and time, theorists say, have to pay their
dues to the uncertainty principle and become fuzzy and
In the last few years, many physicists have pinned their hopes for
quantum gravity on string theory, an ongoing mathematically
labyrinthean effort to portray nature as comprising tiny wiggly
strings or membranes vibrating in 10 or 11 dimensions.
In principle, string theory can explain all the known (and unknown)
forces of nature. In practice, string theorists admit that even
their equations are still only approximations, and physicists
outside the fold complain that the effects of ’’stringy physics’’
happen at such high energies that there is no hope of testing them
in today’s particle accelerators. So theorists have been venturing
into cosmology, partly in the hopes of discovering some effect that
can be observed.
The Big Bang is an obvious target. A world made of little loops has
a minimum size. It cannot shrink beyond the size of the string loops
themselves, Dr. Robert Brandenberger, now at Brown, and Dr. Cumrun
Vafa, now at Harvard, deduced in 1989. When they used their string
equations to imagine space shrinking smaller than a certain size,
Dr. Brandenberger said, the universe acted instead as if it were
getting larger. ’’It looks like it is bouncing from a collapsing
In this view, the Big Bang is more like a transformation, like the
melting of ice to become water, than a birth, explained Dr. Linde,
calling it ’’an interesting idea that should be pursued.’’ Perhaps,
he mused, there could be a different form of space and time before
the Big Bang.
’’Maybe the universe is immortal,’’ he said.
it just changes phase. Is it nothing? Is it a phase transition?
These are very close to religious questions.’’
Work by Dr. Brandenberger and Dr. Vafa also explains how it is that
we only see 3 of the 9 or 10 spatial dimensions the theory calls
for. Early in time the strings, they showed, could wrap around space
and strangle most of the spatial dimensions, keeping them from
In the last few years, however, string theorists have been
galvanized by the discovery that their theory allows for membranes
of various dimensions (’’branes’’ in string jargon) as well as
strings. Moreover they have begun to explore the possibility that at
least one of the extra dimensions could be as large as a millimeter,
which is gigantic in string physics. In this new cosmology, our
world is a three-dimensional island, or brane floating in a
five-dimensional space, like a leaf in a fish tank. Other branes
might be floating nearby. Particles like quarks and electrons and
forces like electromagnetism are stuck to the brane, but gravity is
not, and thus the brane worlds can exert gravitational pulls on each
’’A fraction of a millimeter from
you is another universe,’’ said Dr. Linde. ’’It might be there.
It might be the determining factor of the universe in which you
A New Possibility Is Introduced
That other universe could bring about creation itself, according to
several recent theories. One of them, called branefall, was
developed in 1998 by Dr. Georgi Dvali of New York University and
Henry Tye, from Cornell. In it the universe emerges from its state
of quantum formlessness as a tangle of strings and cold empty
membranes stuck together. If, however, there is a gap between the
branes at some point, the physicists said, they will begin to fall
Each brane, Dr. Dvali said, will experience the looming
gravitational field of the other as an energy field in its own
three-dimensional space and will begin to inflate rapidly, doubling
its size more than a thousand times in the period it takes for the
branes to fall together.
’’If there is at least one region
where the branes are parallel, those regions will start an
enormous expansion while other regions will collapse and
shrink,’’ Dr. Dvali said.
When the branes finally collide, their
energy is released and the universe heats up, filling with matter
and heat, as in the standard Big Bang.
This spring four physicists proposed a different kind of brane clash
that they say could do away with inflation, the polestar of Big Bang
theorizing for 20 years, altogether. Dr. Paul Steinhardt, one of the
fathers of inflation, and his student Justin Khoury, both of
Princeton, Dr. Burt Ovrut of Penn State and Dr. Turok call it the
ekpyrotic universe, after the Greek word ’’ekpyrosis,’’ which
denotes the fiery death and rebirth of the world in Stoic
The ekpyrotic process begins far in the indefinite past with a pair
of flat empty branes sitting parallel to each other in a warped
five-dimensional space -- a situation they say that represents the
simplest solution of Einstein’s equations in an advanced version of
string theory. The authors count it as a point in their favor that
they have not assumed any extra effects that do not already exist in
that theory. ’’Hence we are proposing a potentially realistic model
of cosmology,’’ they wrote in their paper.
The two branes, which form the walls of the fifth dimension, could
have popped out of nothingness as a quantum fluctuation in the even
more distant past and then drifted apart.
At some point, perhaps when the branes had reached a critical
distance apart, the story goes, a third brane could have peeled off
the other brane and begun falling toward ours. During its long
journey, quantum fluctuations would ripple the drifting brane’s
surface, and those would imprint the seeds of future galaxies all
across our own brane at the moment of collision. Dr. Steinhardt
offered the theory at an astronomical conference in Baltimore in
In the subsequent weeks the ekpyrotic universe has been much
discussed. Some cosmologists, particularly Dr. Linde, have argued
that in requiring perfectly flat and parallel branes the ekpyrotic
universe required too much fine-tuning.
In a critique Dr. Linde and his co-authors suggested a modification
they called the ’’pyrotechnic universe.’’
Dr. Steinhardt admitted that the ekpyrotic model started from a very
specific condition, but that it was a logical one. The point, he
said, was to see if the universe could begin in a long-lived
quasi-stable state ’’starkly different from inflation.’’ The answer
was yes. His co-author, Dr. Turok, pointed out, moreover, that
inflation also requires fine-tuning to produce the modern universe,
and physicists still don’t know what field actually produces it.
’’Until we have solved quantum
gravity and connected string theory to particle physics none of
us can claim victory,’’ Dr. Turok said.
In the meantime, Augustine sleeps
May 23, 2001, Wednesday
An article in Science Times
yesterday about ideas on the origin of the universe misstated
the affiliation of Dr. Burt Ovrut, a scientist who speculated
that the Big Bang was ignited by a clash of island universes. He
is at the University of Pennsylvania, not Penn State.